Diabetes and non-healing diabetic foot ulcers are the leading causes of non-traumatic lower extremity amputation in the US. Diabetic foot ulcers fail to heal due to an insufficient blood supply, ischemia, neuropathy, poor glucose control, infection, and other contributing factors. Treatment generally includes debridement, infection control, off-loading, and may include administration of either growth factors (e.g., platelet-derived growth factor (PDGF)) or biologic dressings.
MicroRNAs (miRNAs) are a class of small, endogenous and non-coding RNAs able to negatively regulate gene expression by targeting specific messenger RNAs (mRNAs) and inducing their degradation or translational repression (Ambros, Nature 431:350-355 (2004); Bartel, Cell 136:215-233 (2009)). A recent study has defined mRNA degradation as the predominant mechanistic effect of miRNA on its mRNA targets (Guo et al., Nature 2010; 466:835-840).
MicroRNAs have been implicated in a number of biological processes including regulation and maintenance of cardiac function, vascular inflammation and development of vascular pathologies (see Eva Van Rooij and Eric Olson, J. Clin. Invest. 117(9):2369-2376 (2007); Chien, Nature 447:389-390 (2007); Kartha and Subramanian, J. Cardiovasc. Transl. Res. 3:256-270 (2010); Urbich et al., Cardiovasc. Res. 79:581-588 (2008)). miRNAs have also been reported to be involved in the development of organisms (Ambros, Cell 113:673-676 (2003)) and are differentially expressed in numerous tissues (Xu et al., Curr. Biol. 13:790-795 (2003); Landgraf et al., Cell 129:1401-14 (2007)), in viral infection processes (Pfeffer et al., Science 304:734-736 (2004)), and associated with oncogenesis (Calin et al., Proc. Natl. Acad. Sci. USA 101:2999-3004 (2004)); Calin et al., Proc. Natl. Acad. Sci. USA 99(24):15524-15529 (2002)).
Accordingly, modulating the function and/or activity of microRNAs may present therapeutic targets in the development of effective treatments for a variety of conditions. However, delivery of an antisense-based therapeutic targeting a miRNA can pose several challenges. The binding affinity and specificity to a specific miRNA, efficiency of cellular uptake, and nuclease resistance can all be factors in the delivery and activity of an oligonucleotide-based therapeutic. For example, when oligonucleotides are introduced into intact cells they may be attacked and degraded by nucleases leading to a loss of activity. Thus, a useful antisense therapeutic may have good resistance to extra- and intracellular nucleases, as well as be able to penetrate the cell membrane. Conversely, if on-target effects are undesirable in tissues and sites other than that in which the therapeutic is administered, sensitivity to nuclease degradation may limit distal tissue exposure and activity or limit systemic toxicity.
Thus, there is a need for stable and efficacious oligonucleotide-based inhibitors including those for such miRNAs as, for example, miR-92. There is also a need for identification of biomarkers for miRNA modulators, for guiding treatment decisions. The oligonucleotides of the present invention can have advantages in potency, efficiency of delivery, target specificity, stability, and/or toxicity when administered to a subject.